diff --git a/openbsc/include/osmocom/gprs/Makefile.am b/openbsc/include/osmocom/gprs/Makefile.am
index 66b414f..d39592c 100644
--- a/openbsc/include/osmocom/gprs/Makefile.am
+++ b/openbsc/include/osmocom/gprs/Makefile.am
@@ -1,3 +1,5 @@
 libgb_HEADERS = gprs_bssgp.h gprs_ns.h gprs_ns_frgre.h gprs_msgb.h
 
 libgbdir = $(includedir)/osmocom/gprs
+
+SUBDIRS = protocol